Copolymer of an alkyl acrylate and a glycidyl acrylate where the epoxy group is reacted with a polyamide



United States Patent ()fiice 3,095,402 Patented June 25, 1963 3 095,402 COPOLYMER OF AN ALKYL ACRYLATE AND A GLYCIDYL ACRYLATE WHERE THE EPOXY GROUP IS REACTED WITH A POLYAMIDE Alfred Goldschmidt, El Cerrito, and Frank A. Stuart,

Orinda, Calif, assignors to California Research Corporation, San Francisco, Calif, a corporation of Delaware No Drawing. Filed Mar. 31, 1961, Ser. No. 99,678

3 Claims. or. 260-455) This invention is directed to a novel polymeric composition. More particularly, the invention is concerned with a superior new polymeric composition useful as an ashless detergent for internal combustion engine lubricating oils and as a disbursant for engine fuels and hydrocarbon compositions in general.

Lubricant compositions containing detergents are employed to prevent the deposit of solid materials on engine surfaces which come into contact with the lubricant composition. Such deposits of solid materials tend to interfere with proper circulation of the lubricant composition and also act as abrasives which cause excessive wear of engine parts.

Unfortunately a major proportion of modern engine deposits is attributable to the additive commonly present in lubricant compositions. This is particularly the case with metal-containing additives, such as the metal salt detergents. Such metal-containing additives may form an ash when the lubricant is consumed in the engines and this ash will deposit out on engine surfaces coming in contact with the lubricant composition.

:In accordance with the present invention a superior new ashless detergent polymeric composition having valuable disbursing properties in general has been discovered, namely, the oil-soluble copolymer which comprises (A) at least one alkyl ester of an unsaturated monocarboxylic acid of 3 to carbon atoms having from 4 to 30 carbon atoms in each alkyl group and (B) at least one ester of an unsaturated monocarboxylic acid of 3 to 5 carbon atoms and glycidol, the epoxy ring of the glycidyl portion of the polymer being reacted with a linear polyamide amine containing from about 5 to about 30 amido groups, the molar ratio of the glycidyl portion to linear polyamide chain being approximately 1:1, said copolymer containing from about 5 to about 40 monomer units of (A) for each monomer unit of (B) and having a total molecular weight of at least about 2,000.

The polymeric composition of this invention as described above is unusually elfective in the prevention of engine deposits. There is no metal component in the detergent copolymer of the composition and therefore it is substantially free of ash forming tendencies. This is a particular advantage over conventional detergent compositions which contain organic metal salts to prevent deposits.

The alkyl esters of the (A) monomers in the copolymers of the present invention are preferably alkyl esters of alpha, beta-unsaturated monocarboxylic acids of from 3 to 5 carbon atoms having alkyl groups of at least 4 carbon atoms and more preferably of from 8 to 30 carbon atoms. Representative acids of this type are the acrylic, methacrylic, crotonic, tiglic, angelic, hydrosorbic acids, and the like. Representative alkyl groups are butyl, hexyl, heptyl, octyl, decyl, dodecyl, tridecyl, octadecyl, eicoxyl,

etc. Even more desirable are the alkyl esters of acrylic and methacrylic acids and mixtures thereof containing from 8 to 24 carbon atoms in the alkyl groups. They are found to provide highly superior polymers for lubricant compositions and are obtainable in commercial quantities.

The reaction products of glycidyl esters of unsaturated monocarboxylic acids of 3 to 5 carbon atoms and linear polyamide chains which are employed as the (B) monomers of the copolymers according to the present invention are produced by the reaction of the epoxy group of the glycidyl ester with the terminal amino group of the linear polyamide. This results in a monomeric material which may be conveniently illustrated by the following structural formula:

R2 fi OH R1GH=f3 c-oOHi 3H-0HPNHA in which R and R are hydrogen or alkyl groups containing a total of not more than 3 carbon atoms and (A) is a linear polyamide chain containing from 4 to 29' recurring amide units.

The linear polyamide chains are derived by reaction of amines and acids, such as alkylene diamines and dibasic aliphatic and aromatic acids according to known procedures. For present purposes, two main types are preferred as indicated by the following general structural formula:

in which R is an alkylene group of 4 to 8 carbon atoms or an arylene group, such as o-phenylene, rn-phenylene or p-xylylene, R is an alltylene group of 3 to 6 carbon atoms or an arylene group, R is an alkyl group of from 1 to 18, and preferably 4 to 12 carbon atoms, R is an alkyl group containing 5 carbon atoms, and R is hydrogen or an alkyl group of from 1 to 4 carbon atoms. In the above formula the letter x is the integer indicating the recurring amide units sufiicient to make up the total as set out in the foregoing description.

Linear polyamides illustrative of the two general types mentioned above are those obtained by the reaction of hexamethy-lene diamine and adipic acid. Such linear polyamides are illustrated by the following formula:

Additional linear polyamides are those obtained by reacting alkyl amine, such as 2-ethylhexylamine with caprolactam. Such polyamides are illustrated by the formula:

In the above formula x indicates the number of recurring amide groups as already mentioned above.

In preparing the polymers of the invention it is only necessary that conditions be chosen which insure polymerization and the formation of polymers having suitable oil solubility and polarity. The oil-solubilizing (A) monomers vary somewhat in their solubilizing characteristics. Thus, in some cases it is entirely satisfactory to employ oil-solubilizing (A) ester monomers and glycidylpolyamide (B) monomers in ratios as low as 1:1 in order to obtain monomers which are soluble in oil. (In other cases it is advantageous to raise the ratio of (A) to (B) to a much higher value, for example, about 100:1 in order to obtain a polymer product having optimum oil solubility and polarity characteristics. As a general rule, however, polymers having excellent dispersant characteristics, together with the required oil solubility (which should be at least 0.5 and is preferably as great as 10% by weight of the lubricant composition) can be prepared by employing oil-solubilizing (A) alkyl ester monomers and polar acting glycidyl-polyamide (B) monomers in ratios of from about :1 to about 40:1.

The polymeric dispersants of this invention can be prepared by any one of several methods as known in the art. Briefly, there are three general methods with respect to the mode of attachments of the polyamide chains to the polymeric backbone. As one method, the glycidylpolyamide group may be incorporated in the polymer molecule by reacting a preformed polymer of alkyl ester and unsaturated monocarboxylic acid which would thus contain free carboxyl groups as reactive centers. This copolymer would then be reacted with glycidol following which the epoxy group of the glycidyl radical would be reacted with the terminal amino group of the polyamide chains. In the second method of attachment the glycidyl ester group is introduced as the monomer prepared by (a) reacting glycidol with the unsaturated monocarboxylic acid of 3 to 5 carbon atoms to give the corresponding glycidyl ester which is then polymerized to give a glycidyl ester containing copolymer in which the epoxy groups of the glycidyl radical are suitable for reaction with the amino group terminated polyamide chain or (b) reacting the aforementioned glycidyl ester monomer with the amino terminated polyamide chain prior to polymerization with the oil-solubilizing (A) monomer and any optional (C) polar monomers of types other than the polyamide-glycidyl ester monomers. In a third method of attaching the polyamide chains the glycidol and the amino terminated polyamide chain may be reacted first to give a glycidol-amide reaction product which may be flien attached by reaction with the carboxylic acid reacting centers as described in the first mentioned method.

In each of the above-mentioned methods, it is desirable to employ an excess of the amine terminated polyamide chains in order to avoid cross linking and insure linear oil-soluble polymers. Excess amine terminated polyamide is readily removed by extraction, precipitation, or any other conventional separation process. Such excesses are usually at least three to five-fold and range as high as to 30 times the theoretical amount required to react one mole of the amino-terminated amide with one mole of the epoxy group of the glycidyl ester compound.

When the polymeric additive of this invention, or a suitable polymeric intermediate, is prepared by the reaction of monomeric components, such copolymers can be prepared by conventional bulk, solution, or emulsion methods in the presence of addition polymerization initiators. Preferably, however, the copolymerization is effected in an inert organic solvent such as benzene, toluene, xylene, or petroleum naphtha in the presence of a free radical-liberating type of initiator such as a peroxy compound, for example, benzoyl peroxide, acetyl peroxide, tert. butyl hydroperoxide, di-tert. butyl peroxide, di

benzoyl peroxide, or di-ter't. amyl peroxide, or an azo initiator such as 1,1azodicyclohexane, carbonitrile or alpha,alpha-azodiisobutyronitrile. The catalyst, or polymerization initiator, can be employed in an amount of from about 0.01 to 10%, with a preferred range being from 0.01 to 2%. If desired, the catalyst can be added in increments as the reaction proceeds. Likewise, additional portions of the solvent can also be added from time to time in order to maintain the solution in a homogeneous condition. The temperature of copolymerization varies from about to 300 F. with the optimum temperature for any given preparation depending on the nature of the solvent, the concentration of monomers present in the solvent, the catalyst and the duration of the reaction. Much the same conditions are employed when the copolymerization is effected in bulk rather than in the presence of an inert solvent.

The additives of this invention have apparent molecular weights as determined by standard light scattering methods and viscosity measurements of at least 2,000, and preferably at least 50,000. For practical purposes molecular weights of from 100,000 to 1,000,000 are most suitable from the standpoint of viscosity and other physical characteristics of the polymeric additives.

The following examples are illustrative of typical methods for preparing the glycidyl esterminopolyamide polymeric type additives and intermediates according to the invention.

EXAMPLE I This example illustrates the preparation of an amino group terminated caprolactam polyamide.

In a reaction vessel 113 g. of caprolactam is reacted with 42.7 g. of Z-ethylhexylamine. The reaction mixture is heated to 400 F. over a period of three hours and then maintained at 400 through 450 F. for fourteen hours. The reaction product is stripped of unreacted materials by distillation at 5 mm. of mercury pressure and a maximum temperature of about 420 F.

The reaction product was titrated and determined to have an equivalent weight of 760. This corresponds to an average of 5.5 caprolactam units per molecule in the polyamide chain.

EXAMPLE II In this example the above steps were repeated with g. of caprolactam and 20 g. of Z-ethylhexylamine.

The reaction product has an equivalent weight of 1410. This corresponds to an average of 11.3 caprolactam units in the polyamide chain.

EXAMPLE III This example illustrates the preparation of an intermediate copolymer in which the monomers are mixed dodecyl and octadecyl methacrylates and glycidyl methacrylate.

In a reaction vessel 750 g. of mixed alkyl methacrylates having 60% by weight dodecyl and 40% by weight octadecyl alkyl groups, 14.2 g. of glycidyl methacrylate and 510 g. of benzene are heated to reflux in an atmosphere of nitrogen. The refluxing materials are polymerized over a period of seven hours by the addition of a 2% solution of bis-azoisobutyronitrile in benzene as catalyst which is added at a rate of 3.8 ml. every fifteen minutes.

The polymeric reaction product is precipitated by the addition of a four-fold volume of acetone. A determination of the oxirane oxygen in the glycidyl portion indicates the presence of 1.85 by weight of glycidyl methacrylate in the copolymer. This indicates that the alkyl methacrylate and glycidyl methacrylate are present in a 25:1 mole ratio.

EXAMPLE IV In this example the preparation of a copolymer of alkyl methacrylate and polyamide-glycidyl methacrylate is illustrated.

The mixture of g. of the alkyl methacrylate and glycidyl methacrylate copolymer of Example III in 300 ml. xylene and 60 g. of the caprolactam polyamide of Example I in 120 ml. of dimethyl formamide is refluxed in a reaction vessel equipped with refluxing apparatus. The refluxing of the mixture is carried out over a period of six hours. The reaction mixture is then precipitated three times by the addition of acetone.

The polymeric product obtained in this example upon analysis is 0.83% nitrogen which corresponds to 6.8% by weight of caprolactam polyamide in the copolymer. This shows a ratio of alkyl methacrylate to polyamide of about 30:1.

EXAMPLE V This example illustrates variations in the type of alkyl methacrylate and polyamide-glycidyl methacrylate reaction products.

In a reaction vessel 75 g. of the 20:1 ratio copolymer of mixed dodecyl and octadecyl methacrylate and glycidyl methacrylate of the above-described type, 25 g. of caprolactam polyamide of Example II, 100 ml. of dibutyl ether and 60 ml. of dimethylformamide are mixed. The mixture is refluxed for 26 hours. Following this, the reaction mixture is precipitated three times with methanol.

The polymeric product upon analysis shows 0.65% nitrogen, which is equivalent to 5.5% polyamide. This corresponds to an actual molar ratio of alkyl methacrylate to polyamide-glycidyl methacrylate of 80:1.

The polymeric additives of the invention as described above are evaluated as detergents in lubricating oils in a number of tests. The results of the tests along with a description of the polymeric additives are set out in the following table.

In the tests as described below the base oil is a solvent refined Wax free SAE 30 grade mineral lubricating oil. The polymeric additive is employed in the oil in an amount of 1.0% by weight of polymer based on total composition. The base oil contains 12 mM/kg. of the conventional zinc dialkyl dithiophosphate having mixed butyl and hexyl alkyl groups as a corrosion in high temperature oxidation inhibitor.

In the determination of the piston varnish ratings of the oils, a given lubricating oil composition is tested as the crankcase lubricant in a 6-cylinder Chevrolet engine using a low grade gasoline especially prone to cause engine deposits, the conditions being those defined in the standard FL-2 test procedure as described in the June 21, 1948, report of the Coordinating Research Council. This procedure requires the maintenance of a jacket temperature of 9 F. and a crankcase oil temperature of 155 F. at 2500 r.p.m. and 45 brake horsepower of 40 hours, and therefore closely simulates the relatively cold engine conditions which are normally experienced in city driving. At the end of each test, the engine is dismantled and the amount of engine deposits on the piston determined and expressed as the piston varnish rating. This value is obtained by visually rating (on a scale of 0 to 10, with 10 representing the absence of any deposit) the amount of deposit on each piston skirt and averaging the individual ratings so obtained for the various pistons. Under the conditions of this test, a piston varnish rating of 3.5 is indicative of detergent performance, though preferably this rating should be 4 or above. In the case of the base oil alone without the addition of any additives, it is found that the piston varnish rating is approximately 3.0 On the other hand, as indicated by the [data presented in the table below, when the base oil is compounded with the indicated amounts of a copolymer, greatly superior results are obtained.

6 Table l Piston Varnish Exlalmple Rating Polymeric Dispersant From the tests of the foregoing table it will be seen that the illustrative compositions containing the polymeric lubricating oil additives of this invention possess im. proved detergent properties compared to either the base oils alone, or oils containing other closely related copolymers.

The copolymers of this invention are also useful as dispersants for engine fuels and hydrocarbon compositions in general:

We claim:

1. -An oil-soluble detergent copolymer of (A) an alkyl ester selected from the group consisting of alkyl acrylates and alkyl methacrylates containing 8 to 24 carbon atoms in the alkyl group and (B) an ester of anunsaturated acid selected from the group consisting of acrylic acid and methacrylic acid and glycidol, the epoxy ring of the glycidyl portion of the polymer being reacted with a linear polyamide selected from the group consisting of the polyamide of hexamethylene diamine and adipic acid and the caprolactam polymer obtained by reacting caprolactam and alkyl amine in which the alkyl group contains firom 1 to 18 carbon atoms, said linear polyamide containing from about 5 to about 30 recurring amide units, said copolymer having from about 5 to about 40 units of (A) for each unit of (B), a total molecular weight of at least about 2000 and a solubility in mineral lubricating oil of at ieast about 0.5% by weight.

2. An oil-soluble detergent copolymer of (A) an alkyl methacrylate containing 8 to 24 carbon atoms in the alkyl group and (B) glycidyl methacrylate, the epoxy ring of said glycidyl portion of the polymer being reacted with a caprolactam polymer obtained by reacting caprotlactam and Z-ethylhexylamine, said caprolactam polymer having from 5 to 30 recurring polyamide units, said copolymer containing from about 5 to about 40 units of (A) for each unit of (B), a total molecular weight of at least about 2000 and a solubility in mineral lubricating oil of at least about 0.5 by weight.

3. An oil-soluble detergent copolymer of (A) an alkyl methacrylate containing 8 to 24 carbon atoms in the alkyl group and (B) glycidyl methacrylate, the epoxy ring of said glycidyl portion of the polymer being reacted with a linear polyamide obtained by reacting adipic acid and hexamethylene diami-ne, said polyamide having from- 5 to 30 recurring polyamide units, said copolymer containing from about 5 to about 40 units of (A) for each unit of (B), a total molecular weight of at least about 2000 and a solubility in mineral lubricating oil of at least about 0.5% by weight.

References Cited in the file of this patent UNITED STATES PATENTS 2,729,625 Hurwitz Ian. 3, 1956 2,857,354 Fang Oct. 21, 1958 FOREIGN PATENTS 219,236 Australia Jan. 9, 1958 

1. AN OIL-SOLUBLE DETERGENT COPOLYMER OF (A) AN ALKYL ESTER SELECTED FROM THE GROUP CONSISTING OF ALKYL ACRYLATES AND ALKYL METHACRYLATES CONTAINING 8 TO 24 CARBON ATOMS IN THE ALKYL GROUP AND (B) AN ESTER OF AN UNSATURATED ACID SELECTED FROM THE GROUP CONSISTING OF ACRYLIC ACID AND METHYLACRYLIC ACID AND GLYCIDOL, THE EPOXY RING OF THE GLYCIDYL PORTION OF THE POLYMER BEING REACTED WITH A LINEAR POLYAMIDE SELECTED FROM THE GROUP CONSISTING OF THE POLYAMIDE OF HEXAMETHYLENE DIAMINE AND ADIPIC ACID AND THE CAPROLACTAM POLYMER OBTAINED BY REACTING CAPROLACTAM AND ALKYL AMINE IN WHICH THE ALKYL GROUP CONTAINS FROM 1 TO 18 CARBON ATOMS, SAID LINEAR POLYAMIDE CONTAINING FROM ABOUT 5 TO ABOUT 30 RECURRING AMIDE UNITS SAID COPOLYMER HAVINFG FROM ABOUT 5 TO ABOUT 40 UNITS OF (A) FOR EACH UNIT OF (B), A TOTAL MOLECULAR WEIGHT OF AT LEAST ABOUT 2000 AND A SOLUBILITY IN MINERAL LUBRICATING OIL OF AT LEAST ABOUT 0.5% BY WEIGHT. 